Transmission line transposition



March 5, 1940.

DE WITT R. GODDARD TRANSMISSION LINE TRANSPOSITION I Original Fil'edJan. 11, 1936 Fly @2 Fly. 1

\ 09/1 07 R DOA/5'0 BY 7 INVENTOR I E Z w I ATTORNEY Patented Mar. 5,1940 UNITED STATES PATENT oFFicE De Witt Rugg Goddard, Riverhead, N. Y.,assignor to Radio Corporation of America, a corporation of DelawareApplication January 11, 1936, Serial No. 58,725 Renewed May 18, 1939 14Claims.

This invention relates to a new and novel transmission linetransposition system which is particularly adapted to reception of shortwave signals.

An object of this invention is to provide an improved transmission linehaving an improved spacing member or transposition block to transposethe wires in a manner to give a highly efficient transmission line.

Another object of this invention is to improve a transmission line togive a predetermined surge impedanc by changing the arrangement of thetransmission block.

In the prior art it was customary to use transmission linetranspositions designed to provide as low a capacity between wires aspossible. However, it is occasionally desirable to provide atransmission line with a different surge impedance than that which isobtained by using the ordinary spacing members or transposition blocksfor spacing the wires. In the past when a different surge impedance wasrequired it was customary to place small evenly spaced fixed capacitiesor condensers across the transmission. line thereby loading the line toa new capacity value, thus resulting in a lower surge impedance.

According to my invention, the desired lower surge impedance of thetransmission line is changed by obtaining the desired surge impedancedirectly from the transmission line spacing member itself and notobtaining it from extra capacities added to the transmission line. Ipropose to use several methods of changing the characteristics of thetransposition blocks which are shown in the accompanying drawing inwhich Figure 1 is a plan view of a simple type of transmission block.

Figure 2 is a plan view partly in section of another type oftransmission block similar to that of Figure 1 except that it contains acentral aperture,

Figure 3 is a sectional view of a transmission block having metal platesforming condenser electrodes,

Figure 4 is a plan view of Figure 3,

Figure 5 is a perspective view of a tr'ansmission line havingtransmission blocks arranged to cause certain portions of the impedanceof the line to vary. v

Referring now to Figure 1, a simple type of transmission block I isshown with slots la and grooves lb for retaining the conductors of atwo-wire transmission line. This type of block is similar to those usedin the prior art except that instead of being made of standard ceramicmaterial such as Isolantite it is made of a new ceramic dielectricmaterial known in the trade as Faradite which has a dielectric constantof about 80 Whereas the dielectric constant of a similar block ofIsolantite has a dielectric constant somewhat less than 4. Therefore ifa transmission line using number 1413 and S gauge wire is used with theordinary spacing members the capacity between the wires would be about 2micromicrofarads whereas if the transmission block is made of Faraditethe capacity would be about micromicrofarads. Therefore the use ofFaradite would change the surge impedance of the transmission line withthe transposition members spaced about five feet apart fromapproximately 460 ohms to 200 ohms which is an exceedingly useful valueparticularly when receiving relatively short Wave signals.

In Figure 2 the transmission block 2 of dielectric material is shown tobe of the type having a central aperture-3. According to my invention inorder to change the surge impedance of the line to a lower value a plug4 made of dielectric material having a high dielectric constant ascompared with that of block 2 is arranged to fit within this aperture.Variations of the thickness of the plug 4 with respect to the thicknessof the transmission block 2 and also that of the materials used inmaking this plug will provide a method for easily adjusting the capacitybetween the wires of the transmission line oiiered by the transposition.Also, variations in the diameter of the central aperture and the plugsfrom that of an adjacent block and plug in the transmission line willchange the surge impedance of the line. These plugs may be retainedwithin the aperture by any suitable means such as simple cementing.

In Figures 3 and 4 there is shown a transmission block similar to thatof Fig. 2 except that there are provided metallic plate members 5 and 6which are placed each side of the plug 6 of the transmission block.These metallic plates constitute the plates of a fixed condenser and areprovided with relatively short leads I and 8 which are connected to thewires 9 and In that are being transposed. Transmission line wires 8 andIll are preferably insulated with a high grade insulation material, ormay be bare wire insulated with an interposed sheet of mica between thewires and plates 5 and 6. One of the plates 5 or 6 may be pivotallysecured by any suitable means, such as a. pin la to the iii transmissionblock and arranged to be moved with respect to the other plate toprovide a variable condenser, as indicated by the dash and dot lines inFig. 4.

In the transmission line shown by Figure 5 the mechanical arrangement issuch that the transposition blocks are spaced apart from each other soas to gradually increase in number toward one end of the line thereforethe surge impedance of the line could be made to vary, for example,between the value of ohms the impedance of a half wave doublet and 200ohms the impedance of the pick-up or input coil of a receiver. This sameresult can also be accomplished by maintaining even spacing and varyingthe types of transmission blocks, that is, using blocks having a highercapacity at the point where the doublet antenna is to be connected.

While only a few modifications of this invention have been shown, it isto be distinctly understood that this invention may take other formswithin the spirit and scope of the invention and therefore should not belimited except by such limitations as are imposed in the appendedclaims.

I claim:

1. A transmission line spacing and transposing member comprising a bodyof dielectric material, said spacing member having an aperture, a plugof dielectric material located within said aperture for changing thevalue of surge impedance of said line when desired, the material of saidplug having a dielectric constant greater than that of said spacingmember.

2. A transmission line, a spacing member for transposing said line, saidspacing member being of dielectric material and having a centralaperture, a removable plug of dielectric material located within saidaperture for changing the value of surge impedance of said line whendesired, the material of said plug having a dielectric constant greaterthan that of said spacing memher, the thickness of said plug having apredetermined dimension which difiers from another plug in an adjacentspacing member arranged on said transmission line.

3. A transmission line, a spacing member for transposing said line, saidspacing member being of dielectric material and having a centralaperture, a removable plug of dielectric material located within saidaperture for changing the value of surge impedance of said line whendesired, the material of said plug having a dielectric constant greaterthan that of said spacing member, the diameters of said central apertureand said plug having predetermined dimensions which differ from those ofanother plug in an adjacent spacing member arranged on said transmissionline.

4. A transmission line, a spacing member for transposing saidtransmission line, said spacing member being of dielectric material andhaving a central aperture, a removable plug of dielectric materiallocated within said aperture, the dielectric constant of the material ofsaid plug being greater than that of said spacing member and thematerial of said plug having a predetermined dielectric constant whichdifiers from an other plug arranged on said transmission line.

5. A transmission line spacing member for transposing said transmissionline, said spacing member comprising a plate of insulating dielectricmaterial composed of at least two different solid dielectrics which areplaced in collateral relationship with each other, the surge impedanceof said line being predetermined by a selection of materials ofdifferent electrical properties for both solid dielectrics.

6. A transmission line spacing member comprising a plate of soliddielectric material having an aperture therein, a removable soliddielectric member arranged to fit in said aperture, the surge impedanceof said line being predetermined by a selection of solid dielectricmaterials of different electrical properties for said removable member.

7. A transmission line spacing member com prising a plate of soliddielectric material having a central aperture therein, a soliddielectric member having a different dielectric constant from that ofsaid spacing member and arranged to be cemented in said aperture, thesurge impedance of said line being predetermined by a selection of soliddielectric materials of diiferent electrical properties for said soliddielectric member which is cemented in said aperture.

8. A transmission line spacing member in the form of a parallelepipedfor transposing said line, said spacing member being of solid dielectricmaterial and having a central aperture therein, a removable plug ofdielectric material located within said aperture, a slot adjacent eachone of the corners of said spacing member to retain the Wires of saidtransmission line, the dielectric 1 material of said plug having adielectric constant greater than that of said spacing member.

9. A transmission line spacing member in the form of a parallelepipedfor transposing said line,

said spacing member being of solid dielectric material and having acentral aperture therein, a plug of different dielectric materiallocated within said aperture, a slot adjacent each one of the corners ofsaid spacing member and parallel with its ends to retain the wires ofsaid transmission line, the dielectric material of said plug having adielectric constant greater than that of said spacing member.

10. A transmission line spacing and transposition member comprising abody of dielectric material having an aperture and a removable plug ofdielectric material within said aperture, the material of said plughaving a dielectric constant greater than that of said body.

11. A transmission line spacing and transposition member comprising abody of dielectric material having an aperture and a plug of dielectricmaterial within said aperture, the material of said plug having adielectric constant different than that of said body.

12. A transmission line spacing and transposition member comprising abody of dielectric material having an aperture and a plug of dielectricmaterial within said aperture, the material of said plug having adielectric constant difierent than that of said body, and retainingmeans located on the outside contour of said body for retaining theconductors of a transmission line.

13. A transmission line spacing and transposition member comprising abody of dielectric material having a centrally disposed aperture and aplug of dielectric material within said aperture, the material of saidplug having a dielectric constant different than that of said body, saidbody being slotted for retaining, spacing and transposing a two-wiretransmission line.

14. In combination, a transmission line, a plurality of spacing membersfor transposing and spacing said transmission line, said spacing memofsaid spacing members having a predetermined dielectric constant whichdiffers from the plug of another spacing member arranged on said line.

DE WITT RUGG GODDARD.

